Push-pull mixing circuit for ultrashort waves



June 2, 1942.

M. J. o. STRUTT EI'AL PUSH-PULL MIXING CIRCUITS FOR ULTRA-SHORT WAVES Filed March 21, 1941 lllllll vv xvvv IAH MIT LF. oun ur g INVENTOR S A. VAN DER IE1.

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ATTORNEY v Patented June 2, 1942 Tl PUSH-PULL MIXING cmomr FOR ULTRA- snon'r WAVES Maximiliaan Julius Otto strum, Kornelis Swier Knol, and Aldert Netherlands van der Ziel, Eindhoven.

Application March 21, 1941, Serial No. 384,482 In the Netherlands May 30-, 1940 '1 Claims. (01. 250-20) This invention relates to a push-pull mixing circuit for ultra-short waves and is particularly adapted for use in a superheterodyne receiver for decimeter waves.

' In the reception of ultra-short waves it is necessary to consider the fact that a virtual ohmic resistance of comparatively low value occurs between the control grid and the cathode of an amplifying tube, saidresistance exerting,

appreciable damping on the input circuit. This input damping is brought about partly by the finite transit time of the electronsand partly by the impedances of theelectrode supply-conductors and it may therefore be distinguished in electron damping and conductor damping. A virtual ohmic resistance also occurs between the anode and the cathode, the reciprocal value ofthis resistance being referred to as output damping and being substantially brought about the electrodes. V It is known that the'inputand output damping may be materially decreased by connecting by the "impedances of the supply conductorsfor the consecutive stages of the high-frequency portion of the receiver in push-pull. It is evident thatthe input impedance of a push-pull stage with otherwise unvaried conditions amounts to twice that of a single stage. In a push-pull circuit, however, it is in addition possible for those parts of the electrode supply-conductors in which flows a high-frequency alternating current of the frequency to be amplified, to be made materially shorter than in the case of a single stage so that the damping due to. the conductors is materially decreased. The latter conditionparticularly occurs with the usefof two electrode systems arranged in one tube, or of two separate tubes whose bases are mirror images of one anotherso that they can be directly fastened together.

- On' the ground of the above-stated considerationsit is also advantageous for the mixing stage of a superheterodyne receiver to be made in pushpul1 connection, it then being possible to obtain the additional advantage that no currents a common cathode, the two triodes in push-pull waves has been previously proposed in which the" local oscillations are generated by two push-pull connected triode systems whilst a duo-diode serves as the mixing tube. v

The invention has for its purpose to provide a push-pull mixing circuit of a simple and eflicient construction utilising only a single tube.

According to the invention use .is made of a tube having two electrode systems which are g each constituted by a triode and a diode having connection generating the local oscillations, whilst an impedance across which occur the local oscillations is provided between the two l cathodes, and an impedance across which occur the received oscillations is connected between the two diode. anodes, an oscillatory circuit tuned to the intermediate frequency being arranged intermediate the centres of the two said im pedances.

The invention will be more clearly understood by reference to the accompanying drawing showing, by way of examplaone embodiment thereof.

The circuit shown in the drawing comprises a tube [containing two electrode systems. These electrode systems are respectively constituted by a triode 2; 3, 4 and a diode 5, 4 having acommon having the frequency of the received oscillations or of the oscillator frequency occur in the output impedance so that the risk of troublesomeinterference sound is greatly decreased.

It is known, in addition, that the first detector used in a superheterodyne receiver for ultracathode 4, and by a triode 6, I, 8 and a diode 9, 8 having a common cathode 8. The two triodes in push-pull connection generate the localoscillations, for which purpose the control grids 3 and I are connected via grid condensers l0 and Il to a Lecher wire system l2, l3 which is tuned to the frequencyof the local oscillations with the aid of an earthed bridge 14 whilst an oscillatory circuit l5 tuned to the frequency of the formed by a Lecher-wire system 20, 2| which i is tuned to the frequency of the local oscillations with the aid of a bridge 22.

An oscillatory circuit 23 is provided between the two diode anodes- 5 and 9, said oscillatory circuit being tuned to the frequency of the received oscillations and having its centre earthed. The inductance of this oscillatory circuit is coupled to a coupling coil 24 which is connected to a di-pole aerial or to the output circuit of a highfrequency'amplifying stage so that the received oscillations are inductively transmitted to the circuit 23. V

The bridge 22 is connected to earth via the series-connection of an oscillatory circuit 25 tuned to the intermediate frequency and a network 26 which is constituted by the parallel connection of a resistance and a condenser.

The circuit of the two diodes 4, 5 and 8, 9 consequently comprises an impedance 23 across which occur the received oscillations, and an impedance 20, 2| across which occur the local oscillations whilst the centres of these two impedances are connected together via the seriesconnection of the ciricuit Z5 and the network 26.

The current of the diodes includes a component,

whose frequency is equal to the difference between the frequencies of the received and the local oscillations, which current generates an intermediate-frequency voltage across the circuit 25 anda direct-current component which brings about a direct voltage across the network 25.

The intermediate-frequency circuit 25 may be A coupled to an intermediate-frequency amplifier in order to further amplify the generated intermediate-frequency oscillations.

What we claim is:

1. A push-pull mixing circuit for ultra-short waves, comprising a tube having two electrode systems each of which is constituted by a triode and a diode having a common cathode, circuits connecting the two triodes in push-pull for gen-' erating local oscillations, an impedance across which occur the local oscillations connected between the two cathodes, an impedance across which occur the received oscillations connected between the two diode anodes, and an oscillatory circuit tuned to the intermediate frequency resulting from the interaction of the local and received oscillations connected between the elec-' trical centers of said two impedances. 2. A push-pull circuit as claimedin claim 1, in which the impedance connected between the cathodes is constituted by a Lecher-wire system.

3. A push-pull mixing circuit for ultra-short waves, comprising a tube having two electrode systems each of which is constituted by a triode and a diode having a common cathode, circuits connecting the two triodes in push-pull for gencrating local oscillations, a resonant circuit, uuned to the received oscillations and having its electrical center grounded, connected between the two diode anodes, a Lecher-wire system across which occur the local oscillationsconnected between the two cathodes, and the series-connection between thesliding bridge of the Lecherwire system and ground of an oscillatory circuit tuned to the intermediate frequency, resulting from the interaction of the local and received oscillations, and a network constituted by the parallel connection of a resistance and a condenser,

4. A push-pull mixing circuit for ultra-short waves, comprising a tube having two electrode systems each of which is constituted by a triode and a diode having a common cathode, circuits connecting the two triodes in push-pull for generating local oscillations, said latter circuits comprising a resonant circuit tuned to the local oscillations connected between the anodes of the triodes and a Lecher-wire system connected to the grids of the triodes, a resonant circuit, tuned to the received oscillations and having its electrical center grounded, connected between the two diode anodes, a Lecher-Wire system across which occur the local oscillations connected between the twocathodes, and the series-connection between the sliding bridge of the latter "Lecherwire system and ground of an oscillatory circuit tuned to the intermediate frequency, re-

sulting from the interaction of the local and received oscillations, and a network constituted by the parallel connection of a resistance and a condenser.

5. In a modulator-oscillator circuit for ultrashort waves, the combination with a pair of electrode systems, each comprising at least a cathode, a control grid, an anode and a rectifier anode, an input circuit tuned to the received oscillations connected between the rectifier anodes, circuit means interconnecting the remaining electrodes in push-pull to produce locally generated oscillations, an impedance connecting the two cathodes across which are developed the locally generated oscillations, and a resonant circuit connected between the electrical centers of the input circuit and said cathode impedance,

' said resonant circuit being tuned to the frequency resulting from the interaction of the 10- cal and received oscillations.

6. In a modulator-oscillator circuit, the combination with an electron discharge device containing a pair of electrode systems, each comprising at least a cathode, a control grid and an anode disposed in the order named and a rectifier anode next adjacent the cathode, an input circuit tuned to the received oscillations connected between the rectifier anodes, circuit means interconnecting the cathodes, control grids and anodes in push-pull to produce locally generated oscillations, an impedance connecting the two cathodes across which are developed the locally generated oscillations, and a resonant circuit connected between the electrical centers of the input circuit and said cathode impedance, said resonant circuit being tuned to the frequency resulting from the interaction of the local and received oscillations.

7. In a modulator-oscillator circuit as defined in claim 8 wherein the circuits producing'the local oscillations are constituted by a resonant circuit tuned to said oscillations and connected,

ing bridge of the latter being connected to round through the series-connection of the resonant circuit tuned to the resultant frequency and a network of a resistance and a shunt condenser.

MAXIll/IIIJAAN JULIUS OTTO S'I'RUT'I; KORNELIS SWIER KNOL. ALDERT VAN DER ZIEL. 

